Whangarei Port Evacuated
An ammonia leak has caused the evacuation of a Whangarei port. The fire service was called to Northport at Whangarei Harbour just after 5pm today. Crews were called after workers detected a strong smell of ammonia in the cool stores.
NZ Herald 28.04.2014
Five fire appliances responded to the call, Mr Philips said.
"Two firefighters have donned encapsulated gas suits in an attempt to isolate the leak." The area has been cordoned off and police were helping with evacuations, he said.
The above article is an example of why people in industry monitor & measure Ammonia.
Ammonia (NH3) is a toxic, common, alkaline gas
It’s lighter than air
Its solubility in water causes it to cauterize respiratory tracts, resulting in death at concentrations of 5000 ppm
Anhydrous ammonia is used as a refrigerant in mechanical compression systems as an alternative to the use of ozone-depleting chlorinated and fluorinated refrigerants.
The use of ammonia as a refrigerant (R717) has increased substantially over the past few years.
The global industrial production of ammonia was146 tonnes in 2006 and 198 million tonnes in 2012, a 35% increase.
80% of ammonia produced is used for agricultural purposes
Less than 2% is used for refrigeration.
Large quantities of ammonia can also be found in:
• Fertilizer plants
• Resin production using urea
• Explosives/munitions plants
• Nylon production
• Semiconductor production
• Water and wastewater facilities
• Clandestine drug labs
Refrigeration systems can contain ammonia liquefied under pressure.
Releases of ammonia have the potential to harm people.
If the ammonia leaks while under pressure, larger quantities of the refrigerant may be rapidly released.
Also, some explosions have been attributed to releases of ammonia contaminated with lubricating oil.
Some causes of accidental releases of ammonia
Over pressure conditions
Lifting of pressure relief valves
Seal leaks from rotating shafts and valve stems
Refrigerant piping failures due to loss of mechanical integrity from corrosion
Physical damage of system components from equipment collisions
Hose failures that occur during ammonia deliveries
Incidents resulting in the accidental release of Ammonia have led to:
Injury / Fatalities
Product contaminated with Ammonia
Interruption of refrigeration capacity
Product loss due to refrigeration interruption
Equipment and property damage
Significant financial losses
Ammonia is toxic - harmful if inhaled at high concentrations.
In NZ it is recommended that the TWA (time weighted average) exposure does not exceed 25 ppm.
The Immediately Dangerous to Life and Health (IDLH) level is 300 ppm.
Ammonia is corrosive and exposure will result in a chemical-type burn.
Since ammonia is extremely hygroscopic, it readily migrates to moist areas of the body such as eyes, nose, throat, and moist skin areas.
Exposure to liquid ammonia will also result in frostbite since its temperature at atmospheric pressure is -33 °C.
Any liquid ammonia released to the atmosphere rapidly absorbs moisture in the air and
forms a dense, visible white
cloud of ammonium hydroxide.
The dense mixture tends to travel along the ground
rather than rapidly rising. This behaviour may increase the potential for exposure of workers and the public.
Pure ammonia vapours are not flammable at concentrations of less than 16%, but may be a fire and explosion hazard at concentrations between 16 and 25%.
Oil mixed with Ammonia may reduce the lower flammability limit as low as 8%, depending on the type and concentration of oil.
An important property of ammonia is its pungent odour.
The threshold concentration at which ammonia is detectable varies from person to person; however, ammonia can be usually detected at concentrations in the range of 5 ppm to 50 ppm.
Concentrations above about 100 ppm are uncomfortable to most people; concentrations in the range of 300 to 500 ppm will cause people to leave the area immediately.
Hazard reduction is beyond the scope of this article but if you need to know more the EPA have an article which is a good starting point.
One of their criteria to reduce ammonia hazards is to use ammonia detectors.
These come in the form of fixed detectors or as personal gas monitors.
Facilities should consider installing ammonia detectors in areas where a substantial leak could occur or if the facility is not manned 24 hours/day. The detector will be positioned to allow for the fact that ammonia is lighter than air in its gas state but heavier than air in its anhydrous state.
Ensure that the ammonia detectors are calibrated regularly against a known standard. Check the operation of ammonia sensors and alarms regularly.
Why Measure Ammonia?
While Ammonia's distinctive smell makes it relatively easy to initially identify, the human nose is not calibrated to measure its concentration.
Therefore, real-time monitors are necessary to allow continuous determination of the Personal Protective Equipment (PPE) necessary to provide proper protection from ammonia.
According to the NIOSH pocket guide, protection from low levels of ammonia (up to 250 to 300 ppm) can be as little as a respirator with the appropriate ammonia cartridges.
Entries into concentrations above 300 ppm or into unknown concentrations require positive-pressure supplied air or SCBAs.
Even higher concentrations require full encapsulation suits because of the highly reactive alkaline nature of ammonia gas.
At concentrations above 15% (150,000 ppm), the ammonia atmosphere is potentially explosive, all activity should be stopped and all personnel should leave the area.
Accurate, reliable, and continuous portable ammonia monitors are required to make these decisions.
Choosing the right ammonia sensor
LEL sensors will detect ammonia but over time ammonia will poison the LEL sensor.
Electrochemical sensors can detect small amounts of ammonia but get ‘used up’ when exposed to larger amounts of ammonia.
PID or photoionization sensors are not affected by higher ranges of ammonia & have a faster response time.
In short buyers may find the selection process requires some consideration.
What Measurement Technique Do I use?
The choice of which technique is the best is driven by the expected ammonia concentration and sometimes the solution is using multiple techniques.
For example, the combination of PID with ammonia detector tube is an affordable way of combining inexpensive ammonia specificity (detector tube) with continuous monitoring.
Suggested Measurement Techniques
Know the likely levels you will be measuring as this will help determine your choice of detector.
For example; Levels will always be....
0 to 50 ppm
• Ammonia-specific sensor in MultiRAE Plus or ToxiRAE II or RAE Systems Gas Detection tubes
Frequently over 50 to 100 ppm
• MuitiRAE Plus with PID and ammonia sensor or RAE Systems Gas Detection tubes.
Frequently over 100 ppm
• MuitiRAE Plus with PID, MiniRAE 2000 PID and ToxiRAE PIDs or RAE Systems Gas Detection Tubes.
Choosing an Instrument
If you are unsure - Seek advice as there are different types of instruments on the market and the prices & functionality vary accordingly.
RAE Systems: AP-201
US Environmental Protection Agency